1. Field of the Invention
The present invention relates to a magnetic head for generating a magnetic field to magnetize an external medium, a magnetic head manufacturing method of manufacturing a magnetic head, and an information recording apparatus for recording information on a medium.
2. Description of the Related Art
Recently, as a computer is widely used, a large amount of information is usually dealt with. As one of information recording apparatuses for recording such a large amount of information, there is used a hard disk drive (HDD). Generally, a hard disk drive (HDD) has a magnetic disk which is a disk-like shaped medium for storing information, and a recording head for causing information to be stored in the magnetic disk.
The magnetic disk has a ferromagnetic layer consisting of a ferromagnetic material on a surface thereof. Magnetization is independently maintained on each of microscopic areas of the ferromagnetic layer. The magnetic disk is subjected to a high speed rotation inside the HDD. The recording head has a microscopic recording coil and a pair of magnetic poles. Generally, the recording head is disposed to be adjacent to the magnetic disk. The pair of magnetic poles are placed over against one another with a predetermined interval (gap length) in a direction in which a track of the magnetic disk is extended. The pair of magnetic poles have a predetermined width corresponding to the track width in the track width direction. When a signal current conducts through the recording coil, a magnetic field generates from the recording coil in accordance with the signal current. The magnetic field thus generated is leaked from the pair of magnetic poles, so that magnetization of each track on the surface of the magnetic disk is suitably reversed in a microscopic length unit according to the gap length. Such a reversal of the magnetization causes information to be recorded in form of a direction of magnetization of each microscopic domain.
In order to hold magnetization of each microscopic domain of the magnetic disk thus oriented, there is a need that the ferromagnetic layer of the surface of the magnetic disk has a predetermined or more coercive force Hc. On the other hand, it is needed for a recording head for recording information on the magnetic disk to apply to the magnetic disk such a magnetic field that a magnetic field (a head magnetic field Hh) in the ferromagnetic layer becomes stronger than the coercive force Hc of the magnetic disk so that the respective magnetization of the magnetic disk is reversed.
Generally, the magnetic field generated from the recording head is leaked out of the track as the object of the recording. The leaked magnetic field has an effect on direction and magnitude of magnetization out of the track. Generally, it is considered that intensity of the magnetic field at the lower limit, on which the reversal of magnetization occurs, is xc2xd of the coercive force Hc of the magnetic disk. Thus, in a range that intensity of the magnetic field leaked out of the track as the recording object is not less than xc2xd of the coercive force Hc of the magnetic disk, there is a possibility that the magnetization is reversed also at the out side of the track and whereby recording-stain occurs. The recording-stain is defined in magnitude by a spread in a track width direction as to one end of the range as mentioned above. Generally, the recording-stain becomes relatively larger with respect to the track width, as the track width becomes smaller. Accordingly, the recording-stain is an obstacle to recording information onto the magnetic disk at high recording density. In order to reduce the recording-stain, there is a method of reducing the gap length whereby a leakage of the magnetic field to the out side of the track as the recording object is suppressed.
However, when the gap length is reduced, reversal of magnetization by the recording head in the track as the recording object is performed in the narrow range in the track direction according to the gap length. As the range is narrower, a demagnetizing field of the reversed magnetization is increased, and as a result, intensity of the magnetic field generated from the recording head is weaken by the demagnetizing field. In this manner, when intensity of the magnetic field is weaken, there occurs a shift (a hard transition shift: HTS) of a magnetization transition point at the boundary of an area wherein magnetization is reversed, and as a result, a range in which magnetization is actually reversed, that is, a range in which the recording magnetic field exceeds the medium Hc, is narrowed. This causes overwrite characteristics of recording of information onto the magnetic disk by the recording head, that is, a ratio of reproducing output of information newly recorded to reproducing output of information before overwriting still remained in the event that information is overwritten on the magnetic disk, to deteriorate. As mentioned above, according to the conventional recording head, it is difficult to cope with both reducing the recording-stain and providing excellent overwrite characteristics.
In view of the foregoing, it is an object of the present invention to provide a magnetic head having excellent overwrite characteristics capable of reducing the recording-stain, a magnetic head manufacturing method of manufacturing the magnetic head, and an information recording apparatus having excellent overwrite characteristics capable of reducing the recording-stain.
To achieve the above-mentioned objects, the present invention provides a magnetic head having a pair of magnetic poles disposed to be adjacent to or in contact with a recording medium relatively moving, said pair of magnetic poles being placed over against one another with a predetermined interval in a relative moving direction at an adjacent point or a contact point to the recording medium, in which a magnetic field is generated between the magnetic poles so that the recording medium is magnetized,
wherein a soft magnetic film expanding in a direction blocking facing of the pair of magnetic poles and a non-magnetic film supporting the soft magnetic film are alternately laminated at a position located between the pair of magnetic poles.
In a magnetic head, generally, one or both of a pair of magnetic poles constituting the magnetic head is provided with a sub-magnetic pole at the end wherein the pair of magnetic poles face one another. A spatial distribution of a magnetic field generated between the pair of magnetic poles is controlled by the sub-magnetic pole in accordance with shape, size and material of the sub-magnetic pole. In the event that a magnetic head of the present invention, a magnetic head referred to in a magnetic head manufacturing method of the present invention, which will be described later, and a magnetic head referred to in an information recording apparatus of the present invention, which will be also described later, have such a sub-magnetic pole, the magnetic pole referred to in the present invention implies such a sub-magnetic pole.
Generally, according to a magnetic head, when a predetermined interval is spread between a pair of magnetic poles, HTS is suppressed to be small and an overwrite characteristic is improved. On the other hand, the soft magnetic film is magnetized by a magnetic field generated between the pair of magnetic poles to attract a flux, and thus even in the event that the interval between the pair of magnetic poles is spread, the soft magnetic film serves to suppress a recording-stain in a direction along the recording medium perpendicular to the relative moving direction, that is, a so-called track width direction. Thus, in the event that a predetermined interval is ensured between the pair of magnetic poles, according to the present invention, it is possible to provide a magnetic head coping with both the reduction of the recording-stain and the excellent overwrite characteristic.
In the magnetic head of the present invention as mentioned above, it is preferable that the soft magnetic film has a length with respect to the direction perpendicular to the recording medium, which length is shorter than that of the perpendicular direction of each of the pair of magnetic poles.
Hereinafter, a length of the soft magnetic film and each of the pair of magnetic poles in a direction perpendicular to a surface of the recording medium which a magnetic head is disposed to be adjacent to or in contact with is referred to as a height.
In a magnetic head, generally, a distribution of a magnetic field generated between a pair of magnetic poles of the magnetic head is adjusted by the height of the pair of magnetic poles. However, according to the preferred magnetic head, only varying the height of the soft magnetic film makes it possible to readily adjust the distribution of the magnetic field generated between the pair of magnetic poles, without varying the height of the magnetic poles.
In the magnetic head of the present invention as mentioned above, it is preferable that the soft magnetic film has a thickness of 0.075 xcexcm or less.
The magnetic head of the present invention as mentioned above has the above-mentioned soft magnetic film. Accordingly, the head magnetic field Hh is reduced right under the soft magnetic film and offers the minimum value. Incidentally, generally, the head magnetic field Hh implies intensity of a magnetic field generated from the magnetic head at the central portion of the ferromagnetic layer of the recording medium in the thickness direction.
In a magnetic head in which the soft magnetic film has a thickness of 0.075 xcexcm or less, the reduction of the head magnetic field Hh due to the existence of the soft magnetic film is little, and as will be described later in embodiments of the present invention, the minimum value of the head magnetic field Hh right under the soft magnetic film offers 240 kA/m or more which is considered as coercive force Hc of the magnetic disk now generally used. Thus, it is possible to obtain the excellent overwrite characteristic.
Further, in the magnetic head of the present invention as mentioned above, it is preferable that of the pair of magnetic poles, a non-magnetic film adjacent to the magnetic pole located at the lower stream side with respect to the moving direction of the recording medium relatively moving has a thickness of 0.2 xcexcm or less.
When the thickness of the non-magnetic film is 0.2 xcexcm or less, as will be described in embodiments of the present invention, the recording-stain of the recording head is greatly reduced.
Furthermore, in the magnetic head of the present invention as mentioned above, it is preferable that the soft magnetic film has a size smaller than that of the width direction of the pair of magnetic poles with respect to the width direction along the recording medium perpendicular to the relative moving direction.
Generally, the recording-stain is smaller in the event that the size of the soft magnetic film in the width direction is smaller than the size of the pair of magnetic poles in the width direction, as compared with a case where the size of the soft magnetic film in the width direction is larger than the size of the pair of magnetic poles in the width direction.
Still further, in the magnetic head of the present invention as mentioned above, it is preferable that the soft magnetic film has saturation magnetic flux density not more than saturation magnetic flux density of the magnetic pole located at the lower stream side as to the moving direction of the recording medium relatively moving, of the pair of magnetic poles, and also has saturation magnetic flux density not less than saturation magnetic flux density of the magnetic pole located at the upper stream side as to the moving direction of the recording medium relatively moving, of the pair of magnetic poles.
The soft magnetic film has the saturation magnetic flux density larger than that of the magnetic pole (the lower magnetic pole) located at the upper stream side. This feature makes it difficult to magnetically saturate. Thus it is possible to suppress an increment of the recording-stain due to the saturation. However, in the event that the soft magnetic film 3 is similar to the magnetic pole (the upper magnetic pole) located at the upper stream side in size of the track width direction, there is no need that the soft magnetic film has saturation magnetic flux density which is larger than saturation magnetic flux density of the upper magnetic pole since it does not happen that the flux passes through the soft magnetic film more than the upper magnetic pole. Thus, the recording head, which satisfies this condition, makes it possible to effectively enhance the head magnetic field and thereby suppressing a spread of the recording-stain.
To achieve the above-mentioned objects, the present invention provides a magnetic head manufacturing method for manufacturing a magnetic head having a pair of magnetic poles disposed to be adjacent to or in contact with a recording medium relatively moving, said pair of magnetic poles being placed over against one another with a predetermined interval in a relative moving direction at an adjacent point or a contact point to the recording medium, in which a magnetic field is generated between the magnetic is poles so that the recording medium is magnetized, said magnetic head manufacturing method comprising:
a laminated film forming step of forming a laminated film in which a soft magnetic film and a non-magnetic film supporting the soft magnetic film are alternately laminated on a thin film on which one of said pair of magnetic poles is formed;
a magnetic pole forming step of forming another of said pair of magnetic poles, which is subjected to trimming into the predetermined width by a resist patterning, on a surface of the laminated film formed by said laminated film forming step; and
a trimming step of applying an ion-milling to the laminated film formed by said laminated film forming step and the another magnetic pole formed by said magnetic pole forming step, so that the laminated film is subjected to trimming into the predetermined width while said another magnetic pole is adopted as a mask.
According to the magnetic head manufacturing method of the present invention as mentioned above, it is possible to readily manufacture a magnetic head corresponding to the magnetic head of the present invention, including trimming of the soft magnetic film.
To achieve the above-mentioned objects, the present invention provides an information recording apparatus having a magnetic head disposed to be adjacent to or in contact with a recording medium relatively moving while carrying a magnetization on each point of a surface of the recording medium, wherein information is recorded on each point of the recording medium by reversing a direction of the magnetization,
said magnetic head is a magnetic head having a pair of magnetic poles placed over against one another with a predetermined interval in a relative moving direction at an adjacent point or a contact point to the recording medium, in which a magnetic field is generated between the magnetic poles so that the recording medium is magnetized,
wherein a soft magnetic film expanding in a direction blocking facing of the pair of magnetic poles and a non-magnetic film supporting the soft magnetic film are alternately laminated at a position located between the pair of magnetic poles.
According to the information recording apparatus as mentioned above, the magnetic head has the same structure of the magnetic head of the present invention and has the same effect. Thus, it is possible to expect the excellent overwrite characteristic even in recording of high recording density.
Further, according to the information recording apparatus as mentioned above, it is acceptable that the above-mentioned various type of magnetic heads are adopted as the magnetic head. In this case, the information recording apparatus offers the same effect as the adopted various type of magnetic heads. Thus, it is possible to is expect the excellent overwrite characteristic even in recording of high recording density.
In the information recording apparatus according to the present invention as mentioned above, it is preferable that a thickness of said soft magnetic film is adjusted so that a magnetic field generated between said pair of magnetic poles is a magnetic field not less than a coercive force of the recording medium at the adjacent point or the contact point to the soft magnetic film of the surface of the recording medium.
According to the magnetic head of the information recording apparatus as mentioned above, in a similar fashion to that of the magnetic thin film head of the present invention, there is provided the soft magnetic film. Thus, the head magnetic field Hh is reduced right under the soft magnetic film and offers the minimum value. When the thickness of the soft magnetic film is reduced, the reduction of the head magnetic field Hh due to the existence of the soft magnetic film is little, and as will be described later in embodiments of the present invention, the minimum value of the head magnetic field Hh right under the soft magnetic film is increased. Thus, when the thickness of the soft magnetic film 3 is adjusted so that the head magnetic field Hh right under the soft magnetic film exceeds the coercive force Hc of the recording medium, this makes it easy to perform the flux reversal right under the soft magnetic film. This feature makes it possible to provide excellent overwrite characteristics of recording of the information recording apparatus.